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ORIGINAL ARTICLES |
From the Department of Psychology (C.R.J.), Duke University, Durham, North Carolina; Department of Psychiatry (S.H.B., R.B.W., I.C.S., J.C.B.), Duke University Medical Center, Durham, North Carolina; and Division of Cardiology (D.B.M.), Department of Medicine, Durham, North Carolina.
Address correspondence and reprint requests to John Barefoot, Department of Psychiatry, Behavioral Medicine Research Center, Duke University Medical Center, Durham, NC 27710. E-mail: John.Barefoot{at}duke.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONNOTESREFERENCES |
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Methods: The NEO PI was administered to a sample of 977 coronary catheterization patients with significant coronary artery disease. Over an average 15-year follow-up period, 266 cardiac deaths and 463 total deaths occurred. The relationships of O scores to mortality were examined with Cox proportional hazard models. Each model included age, left ventricular ejection fraction, severity of congestive heart failure, and number of diseased vessels as covariates.
Results: The O domain score was not associated with all-cause mortality and only approached significance for decreased cardiac deaths (p = .055). However, a higher score for Openness to Feelings was associated with a decreased risk of cardiac death (p < .01) and all-cause mortality (p < .01). High Openness to Actions was also associated with decreased cardiac mortality (p < .01) and all-cause mortality (p = .03) risk. Higher Openness to Aesthetics and Ideas were only associated with decreased cardiac death risk (both p values <.04). In contrast, Openness to Fantasy and Values were not associated with longevity. Previous evidence suggested that educational achievement may account for the effects of Openness to Experience on mortality; however, controlling for educational achievement did not change the results.
Conclusion: These findings suggest that greater emotional awareness and high curiosity, as indicated by the NEO PI Feelings and Actions facets, are associated with increased patient longevity independently of other risk factors and educational achievement.
Key Words: mortality • coronary artery disease • personality
Abbreviations: CAD = coronary artery disease; FFM = Five-Factor Model; O = Openness to Experience domain
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INTRODUCTION |
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People who score high on O are described as being more willing to entertain novel ideas and experiences and have unconventional values. These individuals generally experience positive and negative emotions more intensely. In contrast, low scorers behave more conservatively and retain more conventional values and outlooks and experience a narrower range of emotional responses than high scorers (2). Three previous studies have found that the O domain did not predict longevity in healthy elders and patients with chronic renal insufficiency (4–6). However, these studies did not examine the facets of the O domain.
One important factor to consider in any study examining the effect of O on health outcome is that O is moderately associated with cognitive ability and academic performance (7–9). As such, it is possible that O is a proxy measure for educational attainment, which is strongly related to health outcomes and mortality (10–12). Thus, studies investigating the relationship between O and health should control for this potential confound.
The primary goal of the present study was to examine if O or any of its six facets predicted cardiac or all-cause mortality in a large sample of patients with CAD, who were followed for an average of 15 years. In addition to the domain and facet predictors, we included a measure of educational attainment to determine if that accounted for any significant relationships of O or its facets to longevity.
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METHODS |
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Personality Inventory
The O domain and its facets were measured by the 180-item NEO-PI (13). Participants who failed to complete >25% of the items on a scale were removed from analyses. Individuals dropped from analyses due to missing NEO PI data were similar in age and disease severity, but they had lower education (p = .02) than subjects included in the analyses. The domain and facet scores used for analyses were calculated by averaging across the items to control for missing data. Simulations have suggested that averaging the available items provides unbiased estimates and is a reasonable alternative to more complex statistical approaches such as multiple imputation (14). For purposes of comparison, the gender normed T scores for the O domain and facets are presented in Table 1. Facet scales are described in Table 2.
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Procedures
Follow-up of the patients was conducted at 6 months and 12 months after catheterization and annually thereafter. For these analyses, June 2002 was considered the end of follow-up. As of that date, 463 patients had died from all causes, of which 266 were cardiac deaths. Procedures for the documentation of cause of death have been described elsewhere (15). Cardiac deaths were determined on the basis of information provided by the patient’s physician. Cause of death was coded as cardiac or noncardiac by two Duke Clinical Research Institute staff, who had no knowledge of the patient’s scores on the O domain or facet scales. A staff physician resolved any discrepancies in the coding of cause of death between coders. Total mortality and cardiac deaths were the end points used in the present study. Cause of death had not yet been determined for five patients. The average length of follow-up for participants who did not die was 14.68 years (standard deviation = 0.87).
Analyses
The relationships of the O domain and its facets to survival were examined by Cox proportional hazard models. The O domain and each facet were modeled separately. Each model included age and measures of disease severity as covariates to control for confounding. Associations between gender and survival have varied across studies, depending on factors such as patient selection criteria, covariates, and timing of the follow-up period (16,17). Studies using methods similar to those employed in the present study have not observed gender differences in survival (18). To confirm this in the present sample, we tested the association between gender and mortality, controlling for age and clinical indicators of disease. No effect of gender was observed; therefore, it was not included in the main analyses.
Disease severity was indexed by three variables: number of diseased vessels, severity of congestive heart failure, and left ventricular ejection fraction. Effect sizes are reported as hazard ratios comparing a person at the 75th percentile of each scale with the 25th percentile. Thus, effect size is interpreted as the risk of a person in the middle of the upper half of the distribution compared with the risk of a person in the middle of the lower half of the scale’s distribution. In a secondary set of analyses, education—determined by subject’s report of completed years of education—was added to each model examining the relationship between O facets and survival. Due to missing education data, 143 subjects were not included in those analyses. Individuals with and without education data did not differ on O domain or facet scores.
An assumption of the proportional hazards model is that the effect of the predictor (i.e., Openness to Experience and its facets) is constant over time. To test this assumption, we included a time-dependent covariate consisting of the interaction of the predictor variable and the log of survival time in the model. The results of these tests indicated that there were no significant violations of the proportional hazards assumption (all p values >.05).
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RESULTS |
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Educational attainment was strongly correlated with the O domain (r(1,808) = 0.42; p < .01); however, educational attainment did not predict cardiac or all-cause mortality. Furthermore, when controlling for educational attainment, we found no substantial changes in the effects of the O domain and facets on cardiac or all-cause mortality.
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DISCUSSION |
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Past studies did not consider the facets of the O domain. Examination of these lower-level traits showed, independently of age and disease severity, that higher scores on Openness to Feelings and Openness to Actions were associated with longer survival. Follow-up analyses indicated that the significant associations between O facets and mortality were not the result of differences in educational attainment. Our findings that Openness to Feelings and Openness to Actions were related to survival are consistent with previous investigations reporting significant associations between similar constructs—alexithymia and curiosity— and mortality.
Alexithymia, which is characterized by blunted affect and low emotional awareness, is related to mortality risk (19). On its face, Openness to Feelings is a similar construct to Alexithymia and, in fact, is also correlated with the Toronto Alexithymia scale (20). Low emotional awareness may lead to disease via several physiological, behavioral, social, or cognitive mechanisms (21). Low scorers on Openness to Feelings experience a narrower range of affect and are less able to identify their emotions than high scorers (22). Deficits in emotional awareness have been associated with heightened physiological arousal (23) and other known behavioral risk factors such as social isolation (24) and heavy alcohol use (25). In addition, difficulty identifying feelings has been linked to negative affective states such as depression, somatic complaints, and anxiety (26,27).
High scorers on Openness to Actions are willing to explore new experiences and different aspects of self (2), a concept similar to that of curiosity—a psychological trait that has also been linked to mortality (28). Low curiosity may negatively affect health via numerous mechanisms. Individuals scoring low on Openness to Actions (i.e., low curiosity) may be unable to adapt effectively to or accept changes in their routine or environment. Under stress, they may be less likely to cope actively by seeking new friendships or new solutions to current problems (28). Furthermore, low curiosity may indicate aging of the central nervous system (29), one possible biological mechanism leading to the diminished novelty-seeking behavior in this group.
In addition to findings with the Feelings and Actions facets, Openness to Aesthetics and Ideas were also associated with decreased cardiac deaths whereas Fantasy had no association with longevity. In contrast to the protective effects of other O facets, high Openness to Values showed a trend toward increased risk for cardiac deaths. That one facet seemed to be associated with elevated mortality risk, another showed no association, and others were protective may help to explain the previous null results in relationship to the O domain (4–6). It is not clear why high scores on Aesthetics and Ideas and lower scores on Values may have been protective. However, because these effects were weaker, caution should be taken in the interpretation of these results.
The results of this study might be the product of multiple explorative tests; however, considering the significance levels for the effects of the Feelings and Actions facet on mortality, this is unlikely to be the explanation. Replications of the O facet effects on mortality in population samples are needed to determine their generality.
The results of the present study provide new ideas about how personality is related to important health outcomes such as mortality. In addition, the present study shows that examining the lower-order facets of personality, as operationalized by the FFM, enables one to detect relationships that are not captured by higher-order constructs alone. The pattern of results obtained in the current study demonstrates the importance of this approach for future studies.
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NOTES |
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A version of this paper has been presented previously: Jonassaint CR, Boyle SH, Williams RB, Siegler IC, Barefoot JC. Facets of the openness to experience domain predict cardiac death and all-cause mortality. Psychosom Med 2005:67:A90(Abstract 1304). Available at http://www.psychosomaticmedicine.org/cgi/data/67/1/DC1/1.
Received for publication September 3, 2006; revision received January 22, 2007.
DOI:10.1097/PSY.0b013e318052e27d
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